Loop through a comma-separated shell variable

Not messing with IFS
Not calling external command

variable=abc,def,ghij
for i in ${variable//,/ }
do
    # call your procedure/other scripts here below
    echo "$i"
done

Using bash string manipulation http://www.tldp.org/LDP/abs/html/string-manipulation.html

If you set a different field separator, you can directly use a for loop:

IFS=","
for v in $variable
do
   # things with "$v" ...
done

You can also store the values in an array and then loop through it as indicated in How do I split a string on a delimiter in Bash?:

IFS=, read -ra values <<< "$variable"
for v in "${values[@]}"
do
   # things with "$v"
done

Test

$ variable="abc,def,ghij"
$ IFS=","
$ for v in $variable
> do
> echo "var is $v"
> done
var is abc
var is def
var is ghij

You can find a broader approach in this solution to How to iterate through a comma-separated list and execute a command for each entry.

Examples on the second approach:

$ IFS=, read -ra vals <<< "abc,def,ghij"
$ printf "%s\n" "${vals[@]}"
abc
def
ghij
$ for v in "${vals[@]}"; do echo "$v --"; done
abc --
def --
ghij --

I think syntactically this is cleaner and also passes shell-check linting

variable=abc,def,ghij
for i in ${variable//,/ }
do
    # call your procedure/other scripts here below
    echo "$i"
done

#/bin/bash   
TESTSTR="abc,def,ghij"

for i in $(echo $TESTSTR | tr ',' '\n')
do
echo $i
done

I prefer to use tr instead of sed, becouse sed have problems with special chars like \r \n in some cases.

other solution is to set IFS to certain separator

Another solution not using IFS and still preserving the spaces:

$ var="a bc,def,ghij"
$ while read line; do echo line="$line"; done < <(echo "$var" | tr ',' '\n')
line=a bc
line=def
line=ghij

Here is an alternative tr based solution that doesn't use echo, expressed as a one-liner.

for v in $(tr ',' '\n' <<< "$var") ; do something_with "$v" ; done

It feels tidier without echo but that is just my personal preference.

The following solution:

• doesn't need to mess with IFS
• doesn't need helper variables (like i in a for-loop)
• should be easily extensible to work for multiple separators (with a bracket expression like [:,] in the patterns)
• really splits only on the specified separator(s) and not - like some other solutions presented here on e.g. spaces too.
• is POSIX compatible
• doesn't suffer from any subtle issues that might arise when bash’s nocasematch is on and a separator that has lower/upper case versions is used in a match like with ${parameter/pattern/string} or case

beware that:

• it does however work on the variable itself and pop each element from it - if that is not desired, a helper variable is needed
• it assumes var to be set and would fail if it's not and set -u is in effect

while true; do
        x="${var%%,*}"
        echo $x
        #x is not really needed here, one can of course directly use "${var%%:*}"

        if [ -z "${var##*,*}" ]  &&  [ -n "${var}" ]; then
                var="${var#*,}"
        else
                break
        fi
done

Beware that separators that would be special characters in patterns (e.g. a literal *) would need to be quoted accordingly.

Here's my pure bash solution that doesn't change IFS, and can take in a custom regex delimiter.

loop_custom_delimited() {
    local list=$1
    local delimiter=$2
    local item
    if [[ $delimiter != ' ' ]]; then
        list=$(echo $list | sed 's/ /'`echo -e "\010"`'/g' | sed -E "s/$delimiter/ /g")
    fi
    for item in $list; do
        item=$(echo $item | sed 's/'`echo -e "\010"`'/ /g')
        echo "$item"
    done
}

Try this one.

#/bin/bash   
testpid="abc,def,ghij" 
count=`echo $testpid | grep -o ',' | wc -l` # this is not a good way
count=`expr $count + 1` 
while [ $count -gt 0 ]  ; do
     echo $testpid | cut -d ',' -f $i
     count=`expr $count - 1 `
done